{"title":"On regular variation of entire Dirichlet series","authors":"P. Filevych, O. B. Hrybel","doi":"10.30970/ms.58.2.174-181","DOIUrl":null,"url":null,"abstract":"Consider an entire (absolutely convergent in $\\mathbb{C}$) Dirichlet series $F$ with the exponents $\\lambda_n$, i.e., of the form $F(s)=\\sum_{n=0}^\\infty a_ne^{s\\lambda_n}$, and, for all $\\sigma\\in\\mathbb{R}$, put $\\mu(\\sigma,F)=\\max\\{|a_n|e^{\\sigma\\lambda_n}:n\\ge0\\}$ and $M(\\sigma,F)=\\sup\\{|F(s)|:\\operatorname{Re}s=\\sigma\\}$. Previously, the first of the authors and M.M.~Sheremeta proved that if $\\omega(\\lambda)<C(\\rho)$, then the regular variation of the function $\\ln\\mu(\\sigma,F)$ with index $\\rho$ implies the regular variation of the function $\\ln M(\\sigma,F)$ with index $\\rho$, and constructed examples of entire Dirichlet series $F$, for which $\\ln\\mu(\\sigma,F)$ is a regularly varying function with index $\\rho$, and $\\ln M(\\sigma,F)$ is not a regularly varying function with index $\\rho$. For the exponents of the constructed series we have $\\lambda_n=\\ln\\ln n$ for all $n\\ge n_0$ in the case $\\rho=1$, and $\\lambda_n\\sim(\\ln n)^{(\\rho-1)/\\rho}$ as $n\\to\\infty$ in the case $\\rho>1$. In the present article we prove that the exponents of entire Dirichlet series with the same property can form an arbitrary sequence $\\lambda=(\\lambda_n)_{n=0}^\\infty$ not satisfying $\\omega(\\lambda)<C(\\rho)$. More precisely, if $\\omega(\\lambda)\\ge C(\\rho)$, then there exists a regularly varying function $\\Phi(\\sigma)$ with index $\\rho$ such that, for an arbitrary positive function $l(\\sigma)$ on $[a,+\\infty)$, there exists an entire Dirichlet series $F$ with the exponents $\\lambda_n$, for which $\\ln \\mu(\\sigma, F)\\sim\\Phi(\\sigma)$ as $\\sigma\\to+\\infty$ and $M(\\sigma,F)\\ge l(\\sigma)$ for all $\\sigma\\ge\\sigma_0$.","PeriodicalId":37555,"journal":{"name":"Matematychni Studii","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2023-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Matematychni Studii","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.30970/ms.58.2.174-181","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"Mathematics","Score":null,"Total":0}
引用次数: 1
Abstract
Consider an entire (absolutely convergent in $\mathbb{C}$) Dirichlet series $F$ with the exponents $\lambda_n$, i.e., of the form $F(s)=\sum_{n=0}^\infty a_ne^{s\lambda_n}$, and, for all $\sigma\in\mathbb{R}$, put $\mu(\sigma,F)=\max\{|a_n|e^{\sigma\lambda_n}:n\ge0\}$ and $M(\sigma,F)=\sup\{|F(s)|:\operatorname{Re}s=\sigma\}$. Previously, the first of the authors and M.M.~Sheremeta proved that if $\omega(\lambda)1$. In the present article we prove that the exponents of entire Dirichlet series with the same property can form an arbitrary sequence $\lambda=(\lambda_n)_{n=0}^\infty$ not satisfying $\omega(\lambda)